The present invention concerns a thread withdrawal nozzle for an open-end spinning apparatus.
Where open-end spinning is involved, the best thread results are obtained when a thread withdrawal nozzle with a smooth surface is employed. These favorable thread characteristics, however, can only be attained if the thread being withdrawn is strongly twisted. Only with this hard twisted thread, does it become possible to propagate the twisting taking place in the thread withdrawal nozzle back to the point of fiber entwinement. The produced thread, on this account, feels hard to the touch.
In order to improve the propagation of the twist, it is a known practice to provide in the thread change of direction area of the thread withdrawal nozzle, larger projections (DE 31 03 284 A1) or smaller recesses in the form of notches (DE 42 35 024 A1). By these means, the thread is set into vibration during its withdrawal, so that it intermittently contacts the thread removal nozzle inner surface with less force. This enables the achievement that the twisting can propagate itself better from the axial zone of the thread withdrawal nozzle back to the fiber entwinement point of the spinning rotor. Such an arrangement is favorable to the consolidation of the fibers collected on the rotor and an improvement in entwinement is gained. This known thread withdrawal nozzle, with more or less large, i.e. broad, recesses between the projections, indeed leads to such a point that the thread is enabled to exhibit less of a twist. The xe2x80x9clessxe2x80x9d means in comparison with such threads as simply run over a very smooth surface on the thread withdrawal nozzle.
In any case, these projections act, between the larger cut sections or between the narrower notches, very aggressively on the thread which finds itself in the process of withdrawal. An additional fact is that it is not possible to polish or fine-finish the recesses. These profiled thread withdrawal nozzles lead, on this account, to a very rough thread. Further, especially in the case of notches, these openings over time, become clogged, so that their effect on the thread in its state of formation changes, which has a negative result on the spun strength.
Thus a principal purpose of the present invention is to create a thread withdrawal nozzle which enables a good twisting propagation back to the fiber entwinement point, so that a softer thread can be produced without an accompanying roughing of the thread and without changing the conditions of spin when spinning is in operation.
In accord with the features of an embodiment of the invention, a thread withdrawl nozzle is provided for an open-end spinning apparatus possessing a spin rotor, said nozzle having an axial boring, onto which, on the side proximal to the spin rotor, a thread contact surface is attached, on which a thread slides during the withdrawl of said thread out of the spin rotor and in a specified direction of thread travel, therein characterized, in that the thread contact surface possesses several ring-like arranged projections, which respectively between their sides and the thread contact surface, as seen in the direction of travel of the thread, close an obtuse angle xcex1. The projections therein stated aid the twisting propagation, without aggressive action being necessary against the thread, as is the case in the state of the known technology. Much more, the projections act very gently on the thread, so that the surface thereof, during an imparted vibratory motion, is not, or is nearly not, in essence, impaired. Lesser twisting is required for the incorporation of fibers into the thread end, because of the improved twisting propagation in the axial zone of the thread withdrawal nozzle, and there is gained from this situation a soft thread with a smooth surface.
In order, during the imparting of the vibration, not to act too strongly and aggressively, but nevertheless effectively, on the thread, experience has shown, that the invented thread withdrawal nozzle can be further developed wherein the enclosed angle (xcex1) between the side of the projection and the thread contact surface is greater then 110xc2x0. The angle (xcex1) may increase from a side in a direction to the end of the projection remote from the thread contact surface. In one embodiment, the projections exhibit an essentially domed shape or cup-like shape. In this manner, the transitions of the surfaces, with which the thread being withdrawn comes in contact, are not too abrupt, are nicely fared, and protective of the thread. Purposefully, in this respect, a development of the said projections is proposed wherein the projections are constructed from inserted spheres in a partial area of the thread contact surface. The spheres may be non-rotatably affixed.
Experiments have demonstrated that it is of value to dimension the nozzle with a diameter of the domed projection measuring essentially between 1 and 4 mm. The protrusion of the projection relative to the thread contact surface mat be smaller than one-half of the diameter of the bottom surface of the projection which rests on said thread contact surface. The protrusion may not to exceed 0.3 mm. The projections may at least partially rise above a plane in which is located the front surface of the thread withdrawl nozzle proximal to the spin rotor.
Particularly advantageous is a design of the projection wherein the projections, in relation to the thread travel direction, possess, downstream, a steep side, since by means of such a design, the twist propagation completely back to the fiber entwinement point is additionally favored.
By means of an improvement of the thread withdrawal nozzle, wherein the ring-like arranged projections are appointed at equal intervals on the thread contact surface or, the projections are located, at least partially, in a transition zone, the achievement is attained, that in spite of a protective treatment of the thread during the imparting of vibration, a uniform twist propagation back to the fiber entwinement point is gained. Experience has shown, that in the case of the customary size of thread withdrawal nozzles, the arrangement of the projections wherein the diameter pf the circle, on which the projections are placed possesses a value which approaches that of the diameter of the impact plate may be advantageous. The diameter of the circle, on which the projections are placed may be between 7 mm and 12 mm.
For the attainment of a good propagation of twist leading out of the axial longitudinal zone of the thread withdrawal nozzle and back to the fiber entwinement point on the fiber collection surface of the spinning rotor, it is possible to provide different numbers of projections on the radial thread contact surface. However, practice has indicated that too many projections offer no advantage. On this account, it is more practical have a maximum of eight projections, for example four such projections.
Although it is true, that the projections provide a uniform and long lasting influence on the thread while it is forming and being withdrawn, it is of advantage, if, by means of additional measures this said lengthy, unchanging practice is given support. For example, the projections may have an abrasion resistant or polished surface.
The object of the invention can be manufactured in a simple and economical manner. Further, it may be installed by a simple exchange of the previously conventional thread withdrawal nozzle. In spite of the soft action, as compared to the known state of the technology, the invented withdrawal nozzle assures the required vibratory motion and the necessary propagation of the twisting from its place of origin back into the fiber entwinement point, where the twisting is needed. Thereby a smooth and soft thread is produced with good characteristics such as tensile strength, etc. Contrary to the state of the technology, the action of the invented projections does not change with time, since the projections are self cleaning and do not allow deposition of the fibers or the like.
In the following, design examples of the invention are explained with the help of drawings.